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The city of Hillsboro usually schedules clear well cleaning maintenance every three to five years, but because of a back flushing problem, the two tanks at Hillsboro’s Water Treatment Plant were cleaned a year ahead of schedule last week.

“We did some back flushing in and around the water plant and in the process, some sediment blew back into the clear well,” City Administrator Larry Paine said Tuesday. “We thought it a good idea, through a preventive maintenance process, to vacuum out the bottom of those tanks just to keep everything working right.”

Hillsboro’s two tanks, which supply water for the city of Hillsboro and for the city of Peabody, hold water that comes from the Marion Reservoir. The water at the Hillsboro’s Water Treatment Plant is treated, chlorinated, and disinfected before it is sent down the line to the water towers, where pressure and flow is regulated as it is distributed to customers.

“We had some water flow pressure problems at the plant because of the sediment,” Paine said. “But this was an internal problem and did not affect our water service to customers in any way.”

Paine said the city hired a special company that came out with a big truck and trailer. In the trailer were several monitoring screens that showed pictures from a camera mounted on the helmet of the worker who put on a wetsuit and jumped into the tanks.

“The tanks are approximately 10 feet deep, so he was definitely in over his head,” Paine said. “Before he went in, he was completely disinfected so as not to introduce any new bacteria into the tanks.”

Paine said it took several hours to disinfect the bottoms and sides of the tanks with a vacuum-type tool.

“The whole process is very similar to how you would clean a swimming pool,” he said. “He just sucked up the stuff on the bottom and took it out.”

Paine said zebra mussels or drought conditions did not affect city water resources at this time. Cold weather did cause two water lines to break in Hillsboro on Tuesday, but city crews had them fixed by noon the same day.